1. Field of the Invention
This invention relates to a finisher which gives such additional-workings as creasing, folding, punching, stapling and binding to sheets outputted from such image forming devices as printers and copying machines. More particularly, this invention relates to a finisher which gives the sheets the additional-workings, which include at least the mode of folding a sheet to a size smaller than the size of the sheet in the unfolded state, and aligns a sheaf of stacked sheets in a receiving tray unit which stores and stacks sheets.
2. Description of the Related Art
Recently, various finishers which give various additional-workings to sheets with an image formed surface which are outputted from such image forming devices as printer and copying machines, have been proposed. The term "additional-workings" as used herein means various working processes such as sorting sheets, filing sheets with staples, folding sheets in two (double-folding), creasing sheets (creasing), or folding sheets in three or in a cross section like a letter Z (Z-folding), binding sheets with mucilage, and punching sheets for filing. The finisher generally is provided with a receiving tray unit for temporarily storing sheets that have been folded and punched. The sheaf of sheets, which has been stacked and aligned in the receiving tray unit, is conveyed to a stapler and is stapled.
In the field of ordinary printers and copying machines, the end faces of the sheets are aligned along the conveying direction. The alignment is attained by utilizing the weight of sheet, having a transmission gear, or adjusting the angle of a tray U.S. Pat. No. 4,905,053, for example).
The conventional finisher with a stapling mechanism and a sheet folding mechanism aligns a sheet in the conveying direction without reference to the presence or absence of a sheet folding.
The alignment utilizing the weight of a sheet, therefore, encounters many unstable factors and tends to produce an imperfect result.
The alignment which uses a transmission gear only necessary to a small sheet or a folded sheet has such problems as boosting production cost and electric power consumption, and suffering degradation of productivity because of the inability to quickly do the series of additional-workings due to the addition of the transmission gear.
Further, the folded sheet has an unstable shape as compared with an equivalent sheet in an unfolded state because of the presence of the crease of fold. The alignment which uses a tray capable of varying the working angle and necessary only for aligning a folded sheet with an unstable shape, has the problem of boosting manufacturing cost and electric power consumption due to the additional device for the adjustment of the tray angle.